Hernias are any bulges or tears in your pet's body wall that allow body organs and tissue to pass into areas where they do not belong.
Hernias are quite similar to sidewall bulges on an automobile tire. In both situations, a supportive wall has been damage enough to loose its ability to retain contents. Some hernias are minor inconvenience while others are life-threatening conditions. Some are present from birth (congenital) while others are the result of injury or surgery that failed to completely close. When the hernia’s contents can be pressed back into normal position it is called a reducible hernia. After a time, contents of the hernia sac sometimes become "trapped" and can no longer be manually replaced. If the contents of hernias do not receive adequate blood supply the are called a strangulated hernias. Those are an emergency situation.
The umbilicus is your pet’s belly button or navel. Congenital umbilical hernias are the most common of all hernias that veterinarians see. Since this problem may be an inherited trait, some feel that it is best not to breed pets with this condition. Very few breeders take this advice.
Dogs and cats with umbilical hernias have a soft , painless swelling or bulge or bubble over their belly button. The swelling may come and go depending on the pet’s position and how much it has eaten.
Small umbilical hernias contain nothing but a fatty veil we all have in our abdomens called an omentum . It normally covers the intestines like a veil. When pets become obese, their omentum fills with fat.
Small umbilical hernias are not serious. They sometimes close by themselves as young pets mature.. In male dogs and cats, I repair them when the pet is about 12-18 weeks of age - old enough to make the general anesthesia the surgery requires safe. In female pets I spay them right through the defect at 7-8 month of age and sew the hernia shut on my way out. Veterinarians differ in their preferred timing of this surgery. There is a common misconception that cutting the umbilical cord off too close to the body is the cause of this condition. Since genetics plays a part in susceptibility to umbilical hernias, we see them more purebred dogs and cats.
Large umbilical hernias can strangulate (lose their supply of vital oxygen, blood and nutrients) when a loop of intestine or portion of another body organ, gets pinched off or twisted within it. In these cases, the hernia’s fibrous ring squeezes off the blood supply to the strangulated segment of intestine causing cell death and necrosis. As the damaged tissue within the hernia swells with trapped fluid (edema), it is squeezed even tighter. This is a life threatening emergency condition.
Very large hernias are less dangerous then medium size ones. The large ones put no pressure on the intestines and portions of other body organs that may be inside them. They can be a challenge for your veterinarian to close because of a scarcity of available extra tissue to lap over the defect. When hernias do not have sufficient body wall tissue to overlap and sew together soundly, synthetic fabric webbing can be used in dogs and cats just as is done in humans. See the material and techniques here and here.
There is an old doctor's proverb that genetic defects sometimes come in 3's. So when your dog or cat has a major umbilical hernia, ask your vet to check it out for cleft palate, liver shunts and heart abnormalities.
Hernias in the groin commonly occur in female dogs that are pregnant with large litters or experiencing bloating or constipation. Vets occasionally see the problem in male dogs as well. In all cases, tissue that belongs in the rear of the abdominal cavity presses out through a weak area surrounding the femoral artery and nerve. Usually the hernia sac contains nothing but fat. It is reducible back into the abdomen with finger pressure. Under general anesthesia, this sac can be carefully dissect out with scissors and scalpel until it resembles a small balloon attached to the thigh Then it can be carefully replace it into the abdomen. One has to be very cautious when darning the hole shut, not to pinch the femoral artery or nerve. It is quite common for a second hernia form later on the unaffected opposite groin so to be safe, both sides should be carefully checked and any weakness reinforced. Veterinarians occasionally see inguinal hernias in immature pekingeses and other small breeds - too young to be due to the increased abdominal pressure of pregnancy. The condition also occasionally occurs in males. When it does the surgery is the same. Post surgical scaring reinforces and blocks future hernias at the site – if the surgery is done meticulously, it will not reoccur. They must be repaired very delicately so as not to restrict blood flow to the leg. (ref)
Perineal hernias occur just lateral to your pet’s anus. Many more are seen in elderly dogs than in cats. They are most common in male dogs that have not been castrated. In these pets they may occur secondarily to an enlarged prostate - but vets see them in female dogs as well. Some feel that poorly developed muscle mass in the rump area and male hormones predispose to this condition. These hernias can be confused with enlarged or ruptured anal sacs (glands). Inherited weakness in the structures that form the ligamentous ring around the anus are also thought to contribute to this condition. Sometimes only one side is affected but, more commonly, both sides prolapse (bulge) to some degree. One sees this condition most frequently in toy and small breeds. The problem occurs when pets strain to pass hard stools or when a chronically inflamed anal sac causes straining. Sometimes straining (tenesmus) is due to a general inflammation of the anal region. Those pets often scoot. When an enlarged prostate is not the underlying cause, the cause is usually feeding an improper diet. It is usually just fat that works its way into the hernia sac but there are cases in which the bladder or portions of it is also within the hernia sac. When that occurs, the problem becomes a medical emergency because the pet cannot urinate. The contents of the sac can be replaced into the abdomen manually or by elevating the dog or cat’s rear legs. The technique for repair of these hernias is similar to that for femoral hernias. But in these cases, the difficult part is finding enough tissue surrounding the anus to unite with the pelvic structures. It is a difficult tunneling operation because the pelvic bones prevent good exposure of the surgical site. Many veterinarians use non-absorbable suture to darn these defects closed. These sutures stay in the animal for the rest of its life. One must be very careful not to injure the nerves of the rectum and anus during this surgery. The maintenance of sterility during the operation is hard since this is a very contaminated area. Pre and post surgical antibiotics prevent infection. Sometimes two or more operations are required before the defect is completely closed. When one surgically correct this condition it is common to remove the anal sacs as well since they were often the original cause of straining. Again, improper diet is the root of many of these cases. So be sure your pet get plenty of vegetable fiber in its diet and stays well hydrated.
Although diaphragmatic hernias can be congenital (a birth defect), all the ones I have repaired occurred subsequent to car accidents. This problem occurs when, due to collision, pressure within the abdomen suddenly rises, pressing the organs of the abdomen forcefully against the diaphragm and tearing it. This is the most difficult of all hernias to repair. Pets with this condition often come into the hospital gasping for breath. They are reluctant to lie down because on their side, they have even more difficulty obtaining enough oxygen. Often, they become very agitated if their rear legs are elevated. In fact, that is a simple test veterinarians often utilize when they are suspicious a diaphragmatic tear has occurred. X-rays confirm the diagnosis and usually show indistinct areas of the diaphragm at the point of the tear.
In the photograph of the cat at the top of this page, everything between the red and the yellow dotted lines belongs behind the red dotted line (the diaphragm). In that cat, a tear in the diaphragm has allowed organs from the abdomen to press against the heart and squeeze the cat' lungs so that they can not fully inflate. If the x-rays are not as obvious as this one, veterinarians often repeat them after giving the pet an oral dose of barium sulfate. On subsequent x-rays, the barium will outline the track of the intestine and show the veterinarian if the intestine has moved through the tear and into the chest cavity. These tears can be any size. They usually occur where the diaphragm attaches to the rib cage. When this surgery is performed, one must have an assistant breath for the animal. Surgical approach is often quite difficult because the liver and stomach can block access to the region of the tear. But once a tear is repaired the pet can resume a normal life.
Most pericardia-peritoneal hernias occur as a congenital defect (a problem the pet is born with). In this condition, an inherited pathway or tunnel runs from the pet’s abdomen to the sac that surrounds the heart (the pericardial sac). Symptoms of the disease are the same symptoms as heart failure because the intestines that have pass into the pet's chest surround and press on its heart. Repair of such a defect would best be attempted at a large central veterinary specialty practice or university veterinary school.